This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-69192 filed on Mar. 12, 2001 and Japanese Patent Application No. 2001-69191 filed on Mar. 12, 2001.
1. Field of the Invention
The present invention relates to a control system for controlling an electric load, which is driven by electric power supplied from a battery. The present invention particularly relates to such a control system suitable for a vehicle air conditioning system, which air-conditions a passenger room of a vehicle.
2. Description of Related Art
Japanese Unexamined Patent Publication No. 10-157445 discloses a vehicle air conditioning system, which has an electric heater (electric load) driven by electric power supplied from a vehicle battery. Performance of the electric heater is controlled by an electromagnetic relay and an inverter. Furthermore, Japanese Unexamined Patent Publication No. 11-78488 discloses a vehicle air-conditioning system, which has an electric heater driven by electric power supplied from a vehicle battery. It is well known to charge the vehicle battery with the electric power generated by an electric power generating means.
In the above prior art systems, a voltage of the battery largely fluctuates depending on its charge/discharge state. Thus, when the voltage of the battery becomes excessively high, the electric current supplied to the electric heater becomes excessively high. This causes blowing of a fuse connected between the battery and the electric heater. When the fuse is blown, the electric heater can not be used until the blown fuse is replaced with a new one.
Furthermore, in the above systems, when a supply of electric power to each of the electric loads is simultaneously initiated or is simultaneously terminated, a large fluctuation in the voltage of the battery occurs due to a large fluctuation in an electric current at the start or end of the supply of the electric power to each of the electric loads. The large fluctuation in the voltage of the battery can induce a malfunction of another electric load or can deteriorate durability of the electric loads.
Thus, it is an objective of the present invention to address the above disadvantages.
To address the objective of the present invention, there is provided an electric load control system, which charges a battery with electric power generated by an electric power generating means and supplies electric power from the battery to a plurality of electric loads through a fuse. The electric load control system includes a control means, which controls a supply of the electric power to each of the electric loads such that an electric current to the fuse is equal to or less than a tolerable electric current level of the fuse. The supply of the electric power to each of the electric loads is duty controlled by the control means in such a manner that the supply of the electric power to one of the electric loads is phase shifted from the supply of the electric power to another one of the electric loads.
To address the objective of the present invention, there is alternatively provided an electric load control system, which charges a battery with electric power generated by an electric power generating means and supplies electric power from the battery to a plurality of electric loads. The electric load control system includes a control means, which controls a supply of the electric power to each of the electric loads. The supply of the electric power to each of the electric loads is duty controlled by the control means in such a manner that the supply of the electric power to one of the electric loads is phase shifted from the supply of the electric power to another one of the electric loads, so that each power-on time and each power-off time of the one of the electric loads are shifted from each corresponding power-on time and each corresponding power-off time of the other one of the electric loads, respectively.
To address the objective of the present invention, there is also provided an air-conditioning system of a vehicle, which includes any one of the above electric load control systems.